Thesis
Nondestructive detection of post-tensioning tendons and simulated voids in concrete specimens using thermal imaging
Washington State University
Master of Science (MS), Washington State University
2006
Handle:
https://hdl.handle.net/2376/448
Abstract
When post-tensioning steel strands are used in concrete bridges, it is assumed that grout used in the post-tensioning ducts will encase the steel strands and prevent corrosion. However, corrosion of steel strands in grouted post-tensioning ducts has been observed during recent invasive inspections of bridges in Florida and Great Britain. The purpose of this research is to evaluate the use of thermal imaging as a nondestructive inspection method for locating posttensioning steel strands and voids inside grouted ducts embedded in concrete. Two-dimensional finite element models of heat flow through eight previously constructed concrete test specimens were developed. Incremental temperature loadings were applied to one face of the specimens to study the temperature distribution throughout the specimens. Models were developed with both insulated and uninsulated boundary conditions at the edges of the specimens. Experimental testing of six of the concrete specimens was conducted by heating one face of the specimens. The specimens were heated using either solar energy, silicone rubber flexible heating blankets, or an infrared heater. Thermal energy propagation through the thickness of the specimens varied depending on concrete thickness and the embedded materials. This caused surface temperature variations on the concrete specimens that were monitored with a thermal camera. Detection of simulated voids and post-tensioning ducts with 5 cm (2 in) of concrete cover in 20 cm (8 in) thick specimens was possible with a temperature gradient of 11.1°C (20°F) obtained during solar heating and silicone rubber flexible heating blanket tests. Post-tensioning ducts and simulated voids were detected in specimens up to 30 cm (12 in) thick with a 75°C (135°F) temperature gradient using an infrared heater. The post-tensioning ducts were detected in 30 cm (12 in) thick specimens with a maximum of 15 cm (6 in) of concrete cover. Simulated voids were detected when concrete cover was less than 10 cm (4 in). The temperature trends observed for each specimen during the experimental research were very similar to the results predicted from the finite element models.
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Details
- Title
- Nondestructive detection of post-tensioning tendons and simulated voids in concrete specimens using thermal imaging
- Creators
- Ryan Ross Musgrove
- Contributors
- David Garnet Pollock (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525174701842
- Language
- English
- Resource Type
- Thesis